1. Field of the Invention
The present invention relates to a printed circuit board on which a dual inline lead-type electronic part having a plurality of leads is mounted by jet-type soldering using a jet-type solder bath.
2. Description of the Related Art
In general, for a printed circuit board, it has been increasingly required to improve a packing density of parts thereon or miniaturize parts thereon. Therefore, dual inline lead-type electronic parts with narrow pitches or the like have been required to be mounted on the board. On the other hand, practical application of lead-free solder considering environmental problems becomes urgent necessity. However, the lead-free solder is inferior in solderability in comparison with leaded eutectic solder which has been conventionally used. Thus, short circuit at soldered portions between lead terminals of the dual inline lead-type electronic part or the like (referred to as solder bridge) has been occurred.
In order to prevent generation of a solder bridge, conventionally, printed circuit boards using lead-free solder have been made by a method of installing a rectangular-shaped solder-drawing land having a lattice surface and a smooth surface, on the rear side of a soldering land at the rearmost end of a dual inline lead-type electronic part, and allowing the solder-drawing land to absorb excessive solder (see, for example, Japanese Unexamined Patent Application Publication No. 2005-347529 (pp. 4 to pp. 6, FIG. 2 to FIG. 4)).
In addition, as another conventional example, printed circuit boards using lead-free solder have been made by a method of installing a square-shaped solder drawing land having a cross-shaped slit on the rear side of a soldering land at the rearmost end of a dual inline lead-type electronic part and allowing the solder-drawing land to absorb excessive solder (see, for example, Japanese Unexamined Patent Application Publication No. 2007-73747 (pp. 4 to pp. 7, FIGS. 2 and 3)).
As another conventional example, printed circuit boards using lead-free solder have been made by a method of installing a triangle-shaped solder-drawing land on the rear side of a soldering land at the rearmost end of a lead-type electronic part and allowing the solder-drawing land to absorb excessive solder (see, for example, Japanese Unexamined Patent Application Publication No. 2002-280717 (pp. 3 to pp. 4, FIG. 4 to FIG. 6)).